Wyniki wyszukiwania - BazTech

1

Assessment of global ionosphere maps in view of ionospheric correction for coastal and inland altimetry: the case for average total electron content

Jarmołowski Wojciech, Wielgosz Paweł, Krypiak-Gregorczyk Anna, Ren Xiaodong

Meteorology Hydrology and Water Management. Research and Operational Applications

|

2023

|

Vol. 11, Iss. 1

76--92

EN

Several low-Earth orbit (LEO) satellites are equipped with dual-frequency altimeters, theoretically scanning the entire ionosphere in the nadir direction. These two frequencies enable the determination of ionospheric delay and, thus, total electron content (TEC) below the satellite orbit. This information helps in altimetric range determination but is limited to sea and ocean areas. Therefore, global and local ionospheric models are needed for ionospheric corrections over coastal regions and lands. At the same time, altimetry-derived TEC is an important source of validation data for global navigation satellite system (GNSS)-TEC models over the oceans, where the number of GNSS stations is limited. This study compares the application of a high-resolution regional GNSS-TEC model determined from Precise Point Positioning and modeled by least-squares collocation (PPPLSC), and global ionosphere maps (GIMs), in the determination of ionospheric corrections along coastal altimetry tracks. The ionospheric delay values from 5 models are then compared with altimetry-derived TEC from 3 satellites, in the region of southeastern Asia, during a time of moderate TEC values and solar conditions. The reason for the choice of area is that altimetric observations from coastal zones meet difficulties related to atmospheric corrections, e.g., ionospheric correction, which can be affected by the land in the altimeter footprint. For this reason, along with the rapid progress of inland satellite hydrology, we are encouraged to study the consistency of ionospheric delays in coastal regions. The study shows overall discrepancies of 30% of the entire ionospheric delay, which is 2-3 cm even in the case of 35 TEC unit (TECU = 1016 el/m2) values. For this reason, in the case of increased solar activity, the GIMs can have even less TEC consistency with the altimetry-derived TEC, resulting from different orbital altitudes, data gaps, and modeling techniques. The GIMs, modeled by low-order spherical harmonics, have particularly low resolution and do not represent well the equatorial ionization anomaly (EIA).

2

Proposition of Ionospheric Grid in Navigation Satellite System Beidou

Lamparski J.

Annual of Navigation

|

2017

|

No. 24

161--175

EN

This study shows the way of ionospheric data usage obtained from 2 Tables using D2 NAV message Chinese BeiDou system. It was identified particular algorithms for Table’s calculation. Authors also suggested data Table 2 modification and special algorithms useful for that Table. It was given calculated examples for BeiDou system Tables as well as for new suggested system.

PL

W artykule opisano sposób wykorzystania danych jonosferycznych zawartych w dwóch tabelach przesyłanych w depeszy D2 NAV chińskiego systemu BeiDou. Określono szczegółowe wzory umożliwiające określenie danych zawartych w tabelach. Zaproponowano modyfikację tabeli danych nr 2 oraz określono wzory pozwalające na korzystanie z tej tabeli. Podano przykłady liczbowe określenia danych w systemie tabel BeiDou oraz w systemie zaproponowanym.

3

Propagacja fal radiowych w naziemnych i satelitarnych systemach nawigacyjnych

Januszewski J.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

|

2012

|

nr 1

3-9

PL

Sygnały emitowane przez satelity systemów nawigacyjnych (SSN) i systemów wspomagających (SBAS) na swej drodze do odbiornika użytkownika napotykają dwie warstwy atmosfery ziemskiej - jonosferę i troposferę. Omówiono wpływ tych warstw na określanie pozycji użytkownika i jej dokładność oraz podano szczegółowe informacje o poprawkach dotyczących jonosfery, które są przekazywane w depeszy nawigacyjnej satelitów systemów GPS, GLO-NASS, Galileo, OZSS i SBAS. Scharakteryzowano też sposoby propagacji sygnałów emitowanych przez stacje naziemnych systemów radionawigacyjnych, takich jak system Loran C.

EN

The signals transmitted from the satellites of navigation systems (SNS) and augmentation systems (SBAS) on the way to the user's receiver propagate through the two Earth's atmosphere layers - ionosphere and troposphere. The influence of these layers on determination of the user's position and its accuracy and the detailed Information about corrections concerning ionosphere transmitted in the navigation message of GPS, GLONASS, Galileo, OZSS and SBAS satellites are presented in this paper. Additionally the ways of propagation of the signals transmitted from the stations of terrestrial radionavigation systems, as Loran C, are showed also.

4

Study of EGNOS safety of life service during the period of solar maximum activity

Grzegorzewski M., Swiatek A., Oszczak S., Ciecko A., Cwiklak J.

Artificial Satellites : Journal of Planetary Geodesy

|

2012

|

Vol. 47, No. 4

137--145

EN

The Satellite Base Augmentation System (SBAS) - EGNOS (European Geostationary Navigation Overlay Service) has been certified for Safety of Life (SoL) service for aircraft navigation since 2nd of March 2011. Unfortunately for the territory of Poland, located at the edge of EGNOS service area, the quality of the service corrections are still not sufficient for aircraft navigation requirements. Years 2012 and 2013 are forecasted as a maximum of solar activity in a 11-year solar cycle. This time period will be the chance to perform the first tests for the EGNOS Safety of Life service quality in disturbed ionospheric conditions. During the previous maximum of solar activity, the storm on 30 October 2003 resulted in the inability to use WAAS corrections for more than 12 hours. This was caused by a very large gradient of disturbances and its’ very sharp boundaries – vertical TEC (VTEC) varied from ~ 40 to ~ 120 TECU (TEC units) within an hour (over ~ 150 km distance). These circumstances gave the opportunity to carry out the test flights to examine the navigation parameters obtained for EGNOS SoL service in disturbed ionospheric conditions. The paper presents project proposal of study and analyses of such fundamental navigation parameters as: accuracy of determined position, availability, continuity and integrity, determined for selected disturbances in relation to quiet conditions. It can give a possibility to estimate of the quality of EGNOS SoL service in Polish airspace during the different phases of flight and its resistance to critical ionospheric conditions.

5

Ionospheric correction of space radar data

Hapgood M.

Acta Geophysica

|

2010

|

Vol. 58, no. 3

453-467

EN

Radar is a critical tool for maintaining knowledge of the many objects in low Earth orbit and thus for maintaining confidence that societies around the world are secure against a variety of space-based threats. It is therefore important to raise awareness that LEO objects are embedded in the envelope of relatively dense plasma that co-rotates with the Earth (ionosphere-plasmasphere system) and thus accurate tracking must correct for the group delay and refraction caused by that system. This paper seeks to promote that awareness by reviewing those effects and highlighting key issues: the need to customise correction to the altitude of the tracked object and prevailing space weather conditions, that ionospheric correction may be particularly important as an object approaches reentry. The paper outlines research approaches that should lead to better techniques for ionospheric correction and shows how these might be pursued in the context of the EURIPOS initiative.